Dry Eyes and Diabetes Often Go Hand In Hand
High risk of disorder calls for tight control of glucose levels
"Dry Eye Syndrome," also known as keratoconjunctivitis sicca, is one of the most common conditions diagnosed by eye doctors, and people with diabetes have a significantly increased risk for this disorder. In fact, one study shows that those of us with diabetes have a 50% chance of suffering from dry eye. Symptoms include a scratchy sensation – like fine grains of sand are in the eyes, burning, itching, blurred and fluctuating vision, light sensitivity, redness and, paradoxically, increased watering of the eyes. Dry eye is almost always a condition affecting both eyes.
Normal tears consist of three layers: an outer oil layer that prevents evaporation from the surface of the eye, a middle layer mostly made of water, and an inner mucus layer that allows the middle, watery layer to adhere to the naturally water repellant tissue on the eye's surface. A quantitative shortage or qualitative abnormality in any of these three layers can result in symptoms of dry eye, though effective treatment depends upon correctly diagnosing which layer(s) are deficient. Most cases of dry eye are thought to be due to an insufficient quantity of the middle, water layer, which is normally secreted by a large tear gland (the lacrimal gland) under the rim of the upper and outer eye socket (some small, accessory tear glands are located within the eyelids as well).
Research shows that most cases of dry eye associated with diabetes are caused by insufficient production of tears due to "autonomic neuropathy" affecting the nerves that control the lacrimal gland. That is, the same process leading to diabetic peripheral neuropathy that causes symptoms like tingling or burning in the hands and feet, can also affect the involuntary (autonomic) nerves, including those that normally sense dryness and produce moisture to keep the eyes well lubricated (the same essential mechanism that leads to digestive problems common in diabetes, like diabetic gastroparesis). When the cornea, the transparent and extremely sensitive window overlying the colored parts of our eyes is no longer adequately lubricated, the cells of the cornea become damaged and free nerve endings are exposed – leading to the very typical symptoms of dry eye, including pain and reflex tearing. If the nerves of the cornea are severely affected by autonomic neuropathy, patients may have relatively few symptoms (a dangerous situation, because symptoms like pain tell us when something is wrong – if you accidentally put your hand into a fire and it doesn't hurt, the well being of your hand is in serious jeopardy!)
Keeping blood sugar levels as tightly controlled as possible is the first step in preventing and remedying dry eye syndrome associated with diabetes. Not only does chronically high blood glucose lead to autonomic neuropathy affecting the tear gland, it also affects the quality of our tears by increasing the amount of glucose in those tears and disrupting their normal chemical composition, a factor that also contributes to symptoms of dry eye. One study showed that symptoms of dry eye are more common in patients with poor blood glucose control and those who have been diagnosed with proliferative diabetic neuropathy, the most severe form of this sight-threatening disease.
Medical treatment of dry eye includes a variety of techniques, depending upon the underlying cause: artificial tear supplements designed to more or less mimic deficient tear components; medications designed to increase production of tears by the lacrimal gland; blockage of the tear ducts that drain tears out of the eyes and into the nose, either by tear duct plugs or laser cautery (sort of analogous to blocking the drain in your sink – whatever amount of tears your eyes produce are kept on the surface of the eye for a longer period of time); increasing the amount of omega-3 fatty acids in the diet (increased consumption of cold water fish like salmon or dietary supplements), which has been shown to increase the quantity and quality of tears; increasing the humidity of the local environment by wearing moisture goggles or eyeglasses to prevent evaporation, or by using a room humidifier.
Dry Eye Syndrome affects lots of people past the age of 45, particularly post-menopausal women. People with diabetes are also definitely at increased risk for this very annoying and sometimes debilitating condition, and should consult with their eye doctors to be appropriately tested, diagnosed, and treated.
For more information on diabetic eye disease, consult Dr. Chous' book Diabetic Eye Disease: Lessons From a Diabetic Eye Doctor, Fairwood Press, Seattle, 2003.
Read more about Dr. Chous here.
Visit Dr. Chous' website here.
NOTE: The information is not intended to be a replacement or substitute for consultation with a qualified medical professional or for professional medical advice related to diabetes or another medical condition. Please contact your physician or medical professional with any questions and concerns about your medical condition.
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